The present invention relates to a plasma processing apparatus used in a thin film formation process or in a fine processing step, etc. for producing semniconductor elements, liquid crystal display panels, solar batteries and the like.
Increasing efforts have been put forth for a plasma processing apparatus of the type referred to above so as to realize high-accuracy, high-speed, large-area, and low-damage to devices with an aim to endow the devices with a high level of function and reduce costs associated therewith. Particularly, in an attempt to obtain a film quality uniformity for a substrate in a film forming process or in an attempt to secure a size accuracy in a dry etching process employed in fine processing, precise and uniform control of a temperature of the substrate within its plane is strongly required. Therefore, a plasma processing apparatus of a model using a mechanical clamp or an electrostatic attraction electrode as structure for controlling the substrate temperature has been used for the above purpose.
A conventional plasma processing apparatus using an electrostatic attraction electrode will be described below.
By way of example of the prior art, those plasma processing apparatuses are disclosed in Japanese Laid-Open Patent Publications Nos. 63-7287, 2-7520, 3-102820, 10-189544, and 4-100257.
FIG. 5 is a sectional view of a reaction chamber of the plasma processing apparatus disclosed in Japanese Laid-Open Patent Publication No. 4-100257. This plasma processing apparatus will be discussed hereinbelow as a first example of the prior art.
In FIG. 5, a vacuum chamber 131 includes a gas introduction opening 140 connected to an etching gas introduction device 139 and, a vacuum discharge device 141. An electrostatic attraction electrode 133 is set in the vacuum chamber 131 for electrostatically attracting a substrate 132 to be processed. The electrostatic attraction electrode 133 has an insulating layer 133F (shown in FIG. 6) at a front face and a pair of half-round internal electrodes 142 thereinside as shown in FIG. 8. To the electrostatic attraction electrode 133 are connected a d.c. power source 134 for the electrostatic attraction of the substrate 132 to be processed, and a high frequency power feed device 136. The d.c. power source 134 has a switch mechanism 135 for inverting polarities. A quartz glass plate 138 is placed in the vacuum chamber 131 to confront the electrostatic attraction electrode 133, and an ultraviolet ray source 137 is arranged outside of the vacuum chamber 131 to face the quartz glass plate 138. A push mechanism 143 is also provided for moving up and down the substrate 132 to be processed, and to set and separate the substrate to and from the electrostatic attraction electrode 133.
The operation of the thus-constituted conventional plasma processing apparatus 130 will be depicted below.
The substrate 132 is secured to the front face of the electrostatic attraction electrode 133, so that the substrate is brought to a temperature optimum for plasma processing, when positive and negative voltages are applied by the d.c. power source 134, respectively, to the pair of the internal electrodes 142. In this state, a normal plasma process is carried out on the substrate 132.
After completion of the plasma process, residual electric charges remain at the insulating layer at the front face of the electrostatic attraction electrode 133 although the d.c. power source 134 is shut off. As a result, the substrate 132 remains attracted to the electrostatic attraction electrode 133. In order to stably separate the substrate 132 from the electrostatic attraction electrode 133 by the push mechanism 143 without breaking the substrate or causing similar trouble, in this case d.c. voltages with inverted polarities are applied via the switch mechanism 135 to the internal electrodes, thereby negating the residual electric charges at the substrate 132. Thereafter, the substrate 132 is separated from the electrostatic attraction electrode by the push mechanism 143. Then, ultraviolet rays from the ultraviolet ray source 137, e.g. a mercury lamp, are irradiated to a surface of the insulating layer via the quartz glass plate 138, thereby extinguishing the residual electric charges at the surface of the insulating layer. As is described in the publication, however, the residual electric charges cannot be completely removed by the simple application of d.c. voltages of inverted polarities to the internal electrodes. Moreover, if the d.c. voltages are applied for too long a time, the substrate 132 might be conversely attracted to the electrostatic attraction electrode 133 in some cases, thereby hindering the separation resulting from the push mechanism 143 and probably resulting in a problem when the substrate 132 is to be transferred to a next process. Further, the residual attraction resulting from the residual charges varies depending upon a process pressure, a kind of gas, a gas flow rate, a gas flow ratio and the other parameters as plasma process conditions, or by differences of individual substrates.
The electrostatic attraction electrode 133 is not free from dust, which will be depicted with reference to FIG. 6. Reference numeral 133A is a contact part at a face of the electrostatic attraction electrode continuous with an outer peripheral edge part of the substrate 132. Reference numeral 133B is an end part of the contact face of the electrostatic attraction electrode 133 extending perpendicular to the substrate 132, and reference numeral 133D is a part of the electrostatic attraction electrode 133 that is recessed and not to be in contact with the substrate 132. A shape of the recessed part determines a contact area between the electrostatic attraction electrode 133 and the substrate 132 to enable control of a substrate temperature to achieve optimum plasma processing, although the generation and swirl of dust is not taken into account. The substrate itself contains a degree of warp from a point in time when the substrate 132 is sent into the plasma processing apparatus 130. When the predetermined d.c. voltages are suddenly applied to attract the substrate 132, the attraction proceeds in a manner such that the surface of the electrostatic attraction electrode 133 rubs against a warped portion of the substrate, whereby a rear-face of the substrate 132 or the electrostatic attraction electrode 133 is rubbed. Also, since a frictional resistance, when the end part 133B attracts the substrate 132, increases, the rear face of the substrate 132 or electrostatic attraction electrode 133 is rubbed even more. The rubbed portion of the substrate 132 or electrode 133 becomes a dust source, resulting in a decreased yield. The phenomenon is much more noticeable as the substrate is larger in size. Because of the above reasons, the conventional plasma processing apparatus 130 has a problem to be solved with regard to reliability.
The present invention is devised to solve the aforementioned problem and has for its object to provide an apparatus and a method whereby an attraction force generated by residual electric charges between a substrate and a substrate hold stage is reduced so that the substrate and the substrate hold stage can be separated from each other without any problems, irrespective of process conditions, differences of individual substrates, etc., and at the same time the generation and swirl of dust resulting from rubbing of the substrate and the substrate hold stage subsequent to the attraction is prevented.
In accomplishing these and other objects, according to a first aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber for evacuating gas therefrom, for introducing reaction gas therein, and for generating plasma therein through high frequency power application; and
a substrate hold stage set in the vacuum chamber, with the substrate hold stage including a set face having a recessed part, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face.
According to a second aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the first aspect, wherein the set face has an area that is to contact the substrate which is not smaller than 5% and not larger than 15% of a plane area of the substrate.
According to a third aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber for evacuating gas therefrom, for introducing reaction gas therein, and for generating plasma therein through high frequency power application; and
a substrate hold stage set in the vacuum chamber, with the substrate hold stage including a set face, wherein a rear face of a substrate to be subjected to plasma processing is held on the set face, wherein the set face is formed to follow an outer circumferential edge part of the substrate, and wherein the set face is formed of two or more band-like parts or radially-spaced circumferential portions that have an area that is to contact the substrate which is not larger than 10% of a planar area of the substrate.
According to a fourth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber for evacuating gas therefrom, for introducing reaction gas therein, and for generating plasma therein through high frequency power application; and
a substrate hold stage set in the vacuum chamber, with the substrate hold stage including a set face, wherein a rear face of a substrate to be subjected to plasma processing is held on the set face, and wherein the set face is provided with recessed parts of a plurality of depths such that 80% or more of a total area of the recessed parts have a depth smaller than 100 xcexcm and 5-20% of the total area of the recessed parts have a depth of not smaller than 100 xcexcm.
According to a fifth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber for evacuating gas therefrom, for introducing reaction gas therein, and for generating plasma therein through high frequency power application; and
a substrate hold stage set in the vacuum chamber, with the substrate hold stage including a set face, wherein a rear face of a substrate to be subjected to plasma processing held on the set face, and wherein the set face is provided with a recessed part which forms edge part that touches the substrate along a smooth curve.
According to a sixth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber for evacuating gas therefrom, for introducing reaction gas therein, and for generating plasma therein through high frequency power application; and
a substrate hold stage set in the vacuum chamber, with the substrate hold stage including a set face wherein, a rear face of a substrate to be subjected to plasma processing is held on the set face and wherein, an edge part of the substrate hold stage in contact with the substrate is shaped as a semi-circular smooth curve having of a radius of curvature of not smaller than 5 xcexcm.
According to a seventh aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the first aspect, wherein the substrate hold stage includes an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other.
According to an eighth aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the second aspect, wherein the substrate hold stage includes an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other.
According to a ninth aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the third aspect, wherein the substrate hold stage includes an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other.
According to a tenth aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the fourth aspect, wherein the substrate hold stage includes an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other.
According to an eleventh aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the fifth aspect, wherein the substrate hold stage includes an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other.
According to a twelfth aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the sixth aspect, wherein the substrate hold stage includes an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, and wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other.
According to a thirteenth aspect of the present invention, there is provided a plasma processing method comprising:
holding a substrate to be subjected to plasma processing with a rear face of the substrate being held on a set face of a substrate hold stage set in a vacuum chamber;
evacuating gas from the vacuum chamber, introducing reaction gas into the vacuum chamber, and generating plasma in the vacuum chamber through high frequency power application to perform plasma processing of the substrate; and
removing the processed substrate from the set face after completion the plasma processing,
wherein in the holding of the substrate, a d.c. voltage is applied to electrodes in the substrate hold stage while the d.c. voltage is gradually increased to a predetermined value to hold the substrate on the substrate hold stage, and in the removing of the processed substrate, the d.c. voltage is gradually decreased from the predetermined value to remove the processed substrate from the substrate hold stage.
According to a fourteenth aspect of the present invention, there is provided a method for plasma processing according to the thirteenth aspect, wherein in applying the d.c. voltage, the application of the d.c. voltage is carried out at an absolute value of 100V/sec or lower before reaching not larger than 20% of a maximum application value, and is then carried out at a value higher than the absolute value of 100V/sec, whereas in removing the substrate, the d.c. voltage is decreased at a value higher than the absolute value of 100V/sec before reaching not larger than 20% of the maximum application value, and is then carried out at the absolute value 100V/sec or lower to stop the application of the d.c. voltage for removing the substrate.
According to a fifteenth aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber for evacuating gas therefrom, for introducing reaction gas therein, and for generating plasma therein through high frequency power application; and
a substrate hold stage set in the vacuum chamber, with the substrate hold stage including an electrostatic attraction electrode to which positive and negative d.c. voltages are applied by positive and negative d.c. voltage application parts, wherein a rear face of a substrate to be subjected to plasma processing is held on the set face by applying the positive and negative d.c. voltages to the electrostatic attraction electrode to generate charges by which the substrate and the substrate hold stage are attracted to each other, wherein the positive d.c. voltage application part by which the positive d.c. voltage is to be applied is divided into two or more sections, and wherein the negative d.c. voltage application part by which the negative d.c. voltage is to be applied is divided into two or more sections, with the positive voltage sections and the negative d.c. voltage sections to be respectively controlled individually.
According to a sixteenth aspect of the present invention, there is provided a plasma processing apparatus as defined in accordance with the fifteenth aspect, wherein a first of the sections of the positive d.c. voltage and a first of the sections of the negative d.c. voltage charges a vicinity of a center of the substrate, and the remaining second section of the positive d.c. voltage and second section of the negative d.c. voltage charges an outer circumferential portion of the substrate.
According to a seventeenth aspect of the present invention, there is provided a plasma processing method comprising:
holding a substrate to be subjected to plasma processing with a rear face of the substrate being held on a set face of a substrate hold stage set in a vacuum chamber;
evacuating gas from the vacuum chamber, introducing reaction gas into the vacuum chamber, and generating plasma in the vacuum chamber through high frequency power application to perform plasma processing of the substrate; and
removing the processed substrate from the set face after completion of the plasma processing,
wherein in holding the substrate on the substrate hold stage, a d.c. voltage is applied to an electrostatic attraction electrode of the substrate hold stage, thereby charging the substrate in a manner so that the charging is first carried out at a vicinity of a center of the substrate and then spreads towards an outer circumference thereof concentrically with the vicinity of the center, while in removing the substrate from the substrate hold stage, electrification caused by the charging is eliminated by stopping the application of the d.c. voltage to the outer circumferential portion of the substrate and finally stopping the application of the d.c. voltage to the central part of the substrate.
According to an eighteenth aspect of the present invention, there is provided a plasma processing apparatus in accordance with the first aspect, wherein the apparatus is a dry etching apparatus for performing dry etching of the substrate in the vacuum chamber.
According to a nineteenth aspect of the present invention, there is provided a plasma processing method in accordance with the thirteenth aspect, wherein the method is a dry etching method for performing dry etching of the substrate in the vacuum chamber.
According to the present invention, the residual attraction to the substrate to be processed is eliminated and problems in transferring the substrate to be processed are solved, so that the apparatus is enhanced with regard to reliability while exhibiting capability of controlling a temperature of the substrate for optimum plasma processing. Product failures due to the generation and swirl of dust are also avoided. Each apparatus and method in accordance with the above aspects can individually achieve the above effect sufficiently.